Evolution of neural induction and dorsal-ventral axis specification: BMP network involvement in annelids

许多动物都有一个集中的神经系统（CNS），神经细胞（神经元）聚集在一起；人类的大脑和脊髓就是一个例子。这种神经元的排列被认为提供了更好的整合和更复杂的信息处理，但对复杂的中枢神经系统如何在不同的动物群体中产生以及这些中枢神经系统如何相互比较的透彻理解是缺乏的。这个项目通过研究一组研究不足的动物——环节动物蠕虫的中枢神经系统发育来解决这些问题。环节动物对神经发育的研究很重要，因为它们的中枢神经系统具有数千个易于再生的神经元，而其他动物的中枢神经系统要么不能很好地再生（例如人类），要么在其中枢神经系统中没有很多神经元。该项目将更好地理解复杂的中枢神经系统是如何形成的，并将开发几种技术作为科学界的资源，包括在环节动物小头猴（Capitella teleta）中进行CRISPR-Cas9基因编辑。该项目还将支持和培养本科生和研究生以及一名博士后。最后，在这个项目中开发的发现和技术将用于1)增加发育生物学课程的本科项目，2)改善目前与女孩公司的外展工作。Eureka暑期项目，让当地初中女生参与STEM活动，3)为当地高中学生和教师开发、实施和评估一个新的教学模块，旨在促进对中枢神经系统多样性的欣赏，更好地理解动物多样性是如何产生的。关于动物进化的一个关键问题是CNSs是如何进化并促进生物多样性的。在许多具有中枢神经系统的动物中，外胚层的整个区域作为背-腹（D-V）轴规范的一部分获得成为神经的潜力。在脊椎动物和昆虫中，骨形态发生蛋白（Bone Morphogenetic Protein， BMP）信号在这两个过程中都起着重要作用。这就提出了一个问题，即后口动物和原口动物的最后共同祖先是否有中枢神经系统，以及这种动物的神经诱导是否与D-V轴规范有关。为了验证这些假设，需要来自其他分类群的数据，特别是螺旋体，这是两个主要的原始类群之一。本项目将通过研究BMP信号在D-V轴和CNS命运规范中的作用来验证这些假设。项目目标是：1)利用原位杂交和免疫组化技术表征BMP通路组分在C. teleta中的表达动态，确定其保护程度；2)利用BMP蛋白和dorsomorphin在C. teleta中进行功能获得和功能丧失实验，评估BMP信号的祖先作用；3)通过CRISPR-Cas9基因组编辑和morpholino敲低分析C. teleta的功能，评估BMP拮抗剂Chordin的祖先作用。通过研究螺旋体环节动物发育过程中BMP信号的功能，这项工作将有助于我们理解中枢神经系统的进化，以及BMP信号网络在祖先两侧动物D-V轴规范和中枢神经系统形成中的作用。

Many animals have a centralized nervous system (CNS) where neural cells (neurons) are clustered together; an example is the brain and spinal cord of humans. This arrangement of neurons is thought to provide better integration and more sophisticated processing of information, but a thorough understanding of how complex CNSs arose in different animal groups and how these CNSs compare with one another is lacking. This project addresses these questions by examining CNS development in a very understudied group of animals, the annelid worms. Annelids are important for studies of neural development because they have CNSs with thousands of neurons that easily regenerate, unlike other animal CNSs that either do not regenerate well (e.g. humans) or do not have many neurons in their CNS. This project will provide a better understanding of how a complex CNS can form and will develop several techniques as resources for the scientific community, including CRISPR-Cas9 gene editing in the annelid Capitella teleta. This project also will support and train undergraduate and graduate students and a postdoctoral fellow. Finally, the findings and techniques developed in this project will be used to 1) augment undergraduate projects in a developmental biology course, 2) improve current outreach efforts with the Girls, Inc. Eureka summer program to engage local junior-high girls in STEM activities, and 3) develop, implement, and asses a new teaching module for local high school students and teachers that is designed to promote an appreciation of CNS diversity and a better understanding of how animal diversity arose.A key question concerning animal evolution is how CNSs evolved and contributed to organismal diversity. In many animals with a CNS, a whole region of the ectoderm acquires the potential to become neural as part of dorsal-ventral (D-V) axis specification. In vertebrates and insects, Bone Morphogenetic Protein (BMP) signaling plays an important role in both processes. This raises the question of whether or not the last common ancestor of deuterostomes and protostomes had a CNS and whether neural induction was linked to D-V axis specification in this animal. To test these hypotheses, data is needed from additional taxa, especially spiralians, one of two main protostome groups. This project will test these hypotheses by investigating the role of BMP signaling in D-V axis and CNS fate specification in the spiralian annelid Capitella teleta. Project aims are: 1) Determine the degree of conservation of BMP pathway components in C. teleta by characterizing their expression dynamics using in situ hybridization and immunohistochemistry, 2) Assess the ancestral role of BMP signaling through gain- and loss-of-function experiments in C. teleta utilizing BMP protein and dorsomorphin, and 3) Assess the ancestral role of the BMP antagonist Chordin by analyzing function in C. teleta through CRISPR-Cas9 genome editing and morpholino knockdown. By studying the function of BMP signaling during development of a spiralian annelid, this work will significantly contribute to our understanding of CNS evolution and the involvement of the BMP signaling network in D-V axis specification and CNS formation in the ancestral bilaterian.